<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
	<input type="text" placeholder="用户名或邮件地址" name="username" />
<input type="password" placeholder="密码" name="password" />
</body>
</html>
<style>
	*{ margin: 0; padding:0;}
     input[type=text], input[type=password] {
        border-color: #bbb;
        height: 38px;
        font-size: 14px;
        border-radius: 2px;
        outline: 0;
        border: #ccc 1px solid;
        padding: 0 10px;
        width: 250px;
        -webkit-transition: box-shadow .5s;
        margin-bottom: 15px;
    }

        input[type=text]:hover,  input[type=text]:focus, input[type=password]:hover,  input[type=password]:focus {
            border: 1px solid #56b4ef;
            box-shadow: inset 0 1px 3px rgba(0,0,0,.05),0 0 8px rgba(82,168,236,.6);
            -webkit-transition: box-shadow .5s;
        }
    input::-webkit-input-placeholder {
        color: #999;
        -webkit-transition: color .5s;
    }

    input:focus::-webkit-input-placeholder,  input:hover::-webkit-input-placeholder {
        color: #c2c2c2;
        -webkit-transition: color .5s;
    }
</style>

<script>
	
	var a = "15088735393";
a = a.replace(/(?=(\d{4})+$)(\d)/g,"$2 ");
alert(a);

</script>